#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#include <unistd.h>
#include <arpa/inet.h>
#include <netdb.h>

void error_handling(char *msg);

int main(int argc, char *argv[])
{
    int i;
    struct hostent *host;
    struct sockaddr_in addr;
    if ( argc != 2) {
        printf("Usage: %s <IP>\n", argv[0]);
        exit(1);
    }

    memset(&addr, 0, sizeof(addr));
    addr.sin_addr.s_addr = inet_addr(argv[1]);
    host=gethostbyaddr((const char *) &addr.sin_addr, sizeof(addr.sin_addr), AF_INET);
    if (!host) {
        switch(h_errno) {
            case HOST_NOT_FOUND:
                printf("host not found\n");
                break;
            case NO_DATA:
                printf("no data\n");
                break;
            case NO_RECOVERY:
                printf("no recovery\n");
                break;
            case TRY_AGAIN:
                printf("try again\n");
                break;
            default:
                printf("else info\n");
                break;
        }
        error_handling("gethost... error");
    }

    printf("Official name: %s \n", host->h_name);
    for (i = 0; host->h_aliases[i]; i++) {
        printf("Aliases %d: %s \n", i + 1, host->h_aliases[i]);
    }

    printf("Address type: %s \n", 
        (host->h_addrtype == AF_INET) ? "AF_INET": "AF_INET6");
    for (i = 0; host->h_addr_list[i]; i++) {
        printf("IP addr %d: %s \n", i + 1, 
            inet_ntoa(*(struct in_addr *)host->h_addr_list[i]));
    }

    return 0;
}

void error_handling(char *msg)
{
    fputs(msg, stderr);
    fputc('\n', stderr);
    exit(1);
}